pigs are us,
There probably are a few people who can't learn to fly. However, I don't think there is any whatsoever evidence that you are one of them.
50 hours is not that many. Quite a lot of people, especially older ones, take longer than that to go solo. It took me 48 hours, and I was considerably younger than you. But most people who take this long don't boast about it in the regular My First Solo and similar types of threads on PPRuNe.
You've been given good advice so far. Don't fly when you're tired, stressed, or overworked. Work out when is a good time of the week or time of day for you, and make that a priority.
What airfield are you flying from? You live in Worcestershire, so it wouldn't surprise me if it's Shobdon. Great little airfield, but people learning to fly at airfields with only one relatively short runway sometimes take longer. If you're having problems judging things on landing, an airfield with more and longer runways, so that you can always land into wind, might help.
What do YOU think is the problem. You say you can't put the different bits of the circuit together; why? I flew with someone like that, and his problem was that he spent so long thinking what to say on the radio that he was always behind the aircraft. Your problem SOUNDS as though you are simply overloaded at present and just need more practice and to be less stressed. But I'm not a mind reader, and neither are your instructors. To a certain extent, flying training is a DIY activity - YOU need to work out why you are having problems, and maybe what would help.
You say you've had three instructors. Yes, but what three? Were they all relatively inexperienced hourbuilders? A very experienced instructor might be able to pinpoint the problem in a way someone with less instructing hours can't. Have a chat with the CFI, tell him/her what I said if you like, and find someone who can really help, not just babysit you while you fly circuits. If that doesn't work, change flying schools. It's your money and your flying and you have that right.
Don't give up yet. I know several people who thought I'd never get my PPL(A); I did, then got a PPL(H), CPL(H) and FI(H). I know someone else who was in the same situation, changed airfields and got a PPL(A), then PPL(H), twin rating, and I think she's doing (or has maybe finished) a CPL. Someone else who was in that situation teaches commercial pilots for the ATPL. Being a slowish learner doesn't mean you can't do it.
Hang in there and good luck. I look forward to reading about your first solo.
